Re: Excessive wear on trailer tires
Check around at a truck stop and have them suggest a shop that aligns big rigs and trailers. That's what I did with mine and found the alignment was so far off, the trailer was eating tires. After getting everything right, I have had no issues with the new tires. Cost was about $100 for the time and actual work, but well worth it. And get a fully written statement of what the alignment was before and after the shop works on it.
The alignment specialist that worked on my trailer said the majority of boat and camping trailers are out of alignment when they are delivered. He had purchased an Airstream and the axle was out of alignment. He said he burned through the tires in the trip home (I think it was about 200 miles). Remember, these are put together by people with no alignment rack, transported in bulk and hooked up to your tow vehicle. I don't know of any dealer who really checks out trailer alignment ("it came from the factory so it has to be right").
Do you have or can you get back the old tires? You need to have them if you want to make a claim. They are the only evidence you have for a claim. My bet is the shop disposed of them as fast as they could, knowing they could be used against them.